1. Field of the Invention
Embodiments of the invention generally relate to methods and apparatus for forming semiconductor devices. More particularly, embodiments of the invention relate to methods for processing a semiconductor substrate.
2. Description of the Related Art
In the field of integrated circuit and flat panel display fabrication, multiple deposition and etching processes are performed in sequence on the substrate within one or more process chambers of a substrate processing system to form various device design structures. Processes such as etching, physical vapor deposition (PVD), chemical vapor deposition (CVD), chamber cleaning, substrate polishing, and conditioning, etc. are well known in the industry and each process often requires appropriate ways to heat a substrate (e.g., a silicon substrate) disposed within the process chamber.
In general, a silicon substrate (e.g., wafers or glass substrates) is transferred onto a substrate support surface of a substrate support assembly (e.g., a susceptor) inside the process chamber. FIG. 1A illustrates a top view of a substrate support surface of a substrate support assembly 120 within a process chamber. The substrate support assembly 120 may include a heating pedestal having a single heating element 112 embedded therein and connected to an input end and an output end of a power source 114.
The small box in FIG. 1A illustrates that the use of the single heating element 112 generates a single heating zone “A” on the substrate support surface of the substrate support assembly 120. However, because different portions of a substrate may have different heat loss when disposed on the substrate support assembly 120, the use of a single heating zone “A” to heat the surface of a substrate disposed thereon often results in uneven temperature distribution among the center portions and the outer edge portions of the substrate surface. In another words, after a substrate is disposed on the surface of the substrate support assembly 120 and heated by turning on the power source 114, the resulting temperature profile on a substrate surface is often not uniform. It was found that the edge portions of the substrate surface will lose heat easily being at lower temperatures than the center portions. The within-wafer temperature non-uniformity can vary up to 6-8 degrees Celsius.
FIG. 1B illustrates a top view a surface of another prior art substrate support assembly 140. The substrate support assembly 140 may include two (2) heating elements 112A, 112B embedded therein and connected to the input ends and the output ends of two (2) power sources 114A, 114B, respectively to improve the within-wafer temperature non-uniformity as discussed above. The small box in FIG. 1B represents two (2) heating zones “A” and “B” on the surface of such prior art substrate support assembly 140, when the two heating elements 112A, 112B are employed. The heating zone “B” generally use higher electrical power input from the power source 114B in order to compensate heat loss on the outer edge portions of the surface of a substrate, when the substrate is disposed on the substrate support surface of such prior art substrate support assembly 140.
However, when multiple heating elements (at least two heating elements are shown in FIG. 1B to generate two heating zone “A” and “B”) are used to generate multiple temperature heating zones (multi-zones) in such prior art substrate support assembly 140, multiple power controllers, multiple cables, and multiple power sources (at least two power sources 114A, 114B are shown in FIG. 1B) must be coupled to these heating elements. At least one power controller and one power source need to be dedicated to each heating element. Thus, the design of such multi-zone substrate support assembly 140 represents undesirable large burdens on software control and hardware design.
Further, when multiple power sources are used to adjust heating temperature outputs of these heating elements, mechanically, each power source would require at least two times (2×) the number of electric cables and mechanical accessory hardware (e.g., at least one input line/end and at least another output line/end for each power source are connected to each heating element). All of these power input and output lines/ends have to be packed inside a support pedestal (e.g., a shaft) of the substrate support assembly, making the pedestal design too bulky and increasing mechanical design burdens. Thus, there is a need for a substrate support assembly with reduced mechanical parts and simple mechanical design.
Still further, the output temperatures among the different temperature zones of such multi-zone substrate support assembly 140 are controlled by fixed electric inputs of the power sources (with each power source connected to each heating element in each zone) and are often difficult to adjust all of them once substrate processing has started. Thus, there is a need for a substrate support assembly capable of adjusting heating outputs in wide temperature ranges and multiple heating zones during substrate processing.
Therefore, there is a need for an improved substrate support assembly with simple heating element design and improved substrate heating efficiency, and still capable of adjusting its surface temperature among multiple adjustable heating zones within a substrate support assembly of a substrate processing system.